Correlation Of Sandstones Research Articles

Correlation of sandstones using heavy minerals: an example from the Statfjord Formation of the Snorre Field, northern North Sea

Abstract Correlation of sandstones using heavy minerals is dependent on the recognition and quantification of provenance-sensitive parameters. Suitable criteria include ratios of minerals that have similar hydraulic and diagenetic behaviour, and properties of populations of individual mineral species. Sandstones of the Statfjord Formation in the Snorre Field display marked variations in their heavy mineral assemblages. Although hydraulic and diagenetic processes have played some part in generating these variations, major changes in the nature of the source material can be detected on the basis of heavy mineral ratio and varietal data. These changes in sand provenance can be used to produce a detailed stratigraphic breakdown of the sequence and to correlate from well to well. Eleven heavy mineral zones have been recognized on the basis of variations in monazite/zircon, garnet/zircon and rutile/zircon ratios, on the incoming of chloritoid, and on the composition of garnet populations. The marked changes in provenance result from the proximity of the depositional location to the hinterland and it is considered unlikely that the detailed correlation made in the Snorre Field area applies to Statfjord sandstones in other parts of the northern North Sea. However, there is evidence for some degree of allogenic control on the heavy mineral variations and therefore some events may have regional significance.

Coal-Bed Methane Resources and Subsurface Definition of the Middle Pennsylvanian Allegheny Formation in Northern West Virginia

Traditional correlation methods have not proven effective in the subsurface definition of the Allegheny Formation. Sandstones are discontinuous, of channel fill origin, and have log signatures that are not uniquely traceable on a regional basis. Erosion and/or non-deposition associated with fluvial-deltaic channels were responsible for observed coal-bed discontinuities and resulted in preservation of incomplete depositional sequences. Lowermost Allegheny Formation and underlying Pottsville Group sandstones often coalesce and/or split. The regional unconformity between Mississippian and Pennsylvanian systems effectively prohibits correlation of sandstones above the middle Mississippian Greenbrier Limestone due to gross variations in sediment thickness and lithology. In the overlying Conemaugh Group, core descriptions are helpful in locating marine zones and red beds, which may then be located on geophysical logs and used in correlations. The combined use of data from coal exploration core holes, gamma-ray and density logs, oil and gas well drillers' logs, and interval thicknesses derived from outcrop studies has allowed tentative subsurface definition of the Allegheny Formation. The number and thicknesses of Allegheny coal beds, associated sandstones, and reported gas shows have been mapped for use in future coal-bed methane development. The West Virginia Geological and Economic Survey developed this integrated approach to correlation while studying themore » coal-bed methane potential of the Allegheny Formation in northern West Virginia under contract to the Texas Bureau of Economic Geology and funded by the Gas Research Institute.« less

The Effects of the Petrology and Diagenesis of Mixed Provenance Sand-stones on Permeability Heterogeneity and Reservoir Characterization

The Comodoro Rivardavia Formation of the north flank of the San Jorge basin is a fluvial/alluvial fan sequence deposited during the late sag stage of rift basin development. Basin fill was derived from eroding volcanic arc to the west and northwest, contemporaneous volcanism, and the basement found to the north. Three petrofacies are recognized: a dominant petrofacies derived from plutonic, volcanic, and metasedimentary rocks (Q{sub 27}F{sub 21}L{sub 52}); a monolithologic volcanogenic sandstone composed entirely of volcanic detritus (Q{sub 6}F{sub 25}L{sub 69}), and a petrofacies recognized as a diagenetically (meteoric) altered derivative of a mixed provenance petrofacies (Q{sub 48}F{sub 9}L{sub 43}). Lateral and vertical variation of sandstone composition provides independent constraints on correlation of sandstones across a portion of the north flank. Factors which govern the diagenesis of the sandstones include burial history, compositional variations, meteoric influx, and presence and compositional variation of infiltrated material. Formation of late smectite as a result of uplift of the basin has increased heterogeneity of permeability. The meteorically altered sandstones have permeabilities that vary three orders of magnitude more than those sandstones that were not strongly leached. Infiltration of fines has reduced permeability, although the composition and extent of infiltration varies greatly. These postdepositional processesmore » have played an important role in determining reservoir heterogeneity.« less

Further comment on correlation of Sandstones at Billinge Beacon

Discussion a propos de l'article Lower delta plain interdistributary deposits: an example from the Westphalian of the Lancashire Coalfield, northwest England de Fielding (C. R.) paru dans Geological Journal, 1987, 22, 151-162

Determination of Widths of Meander-Belt Sandstone Reservoirs from Vertical Downhole Data: ABSTRACT

Once it has been determined that a meandering fluvial model is applicable to a formation, paleohydrologic reconstructions can be applied to downhole measurements to derive sand body widths. The nonmarine part of the Mesaverde Formation in the east-central part of the Piceance Creek basin of northwestern Colorado was deposited in a predominantly meandering fluvial End_Page 505------------------------------ system. This interpretation is based on the presence of lateral accretion beds and multi-story sand bodies in outcrops along the Grand Hogback. It is supported by fining-upward trends in cores and gamma ray logs from the wells of the U.S. Department of Energy's Multi-Well Experiment being conducted near Rifle, Colorado. Paleochannel depths, recognized from the heights of fining-upward trends in cores, can be converted to channel widths using Leeder's 1973 formula. The resulting channel widths are used to calculate meander belt amplitudes (sandstone body widths) from relationships derived from Leopold and Wolman's 1960 empirical data. These numbers can be compared with sandstone body widths derived by two other methods. (1) Point-bar dimensions measured in outcrops can be used to calculate channel widths, which are then converted to meander-belt amplitudes as described above. (2) The MWX-2 well is offset from MWX-1 by 135 ft (41 m) at the surface, allowing for positive well-to-well correlation of sandstones. The percentage of sandstones which are penetrated by both wells is used as a probability to derive an average sand body width. These last two methods give compatible results. The first method described, however, predicts comparatively narrow widths, suggesting that channel depths derived from fining-upward sequences in cores are not fully representative of ancient channel depths due to incomplete preservation. A preservation potential factor may be added to Leeder's formula for working with ancient sediments, so that the formula gives comparable results to the other two methods. End_of_Article - Last_Page 506------------

Petrography and correlation of sandstones in the New Red Sandstone (Permo-Triassic) of Arran

Synopsis Petrographic data on the lithic sandstones in the New Red Sandstone of Arran are presented. Fibrous chert (agate) appears to be confined to a belt of outcrop running across the island from east to west. It is suggested that the base of the agate-bearing rocks may represent the nearest approach to a time plane in a succession in which correlation is otherwise both broad and uncertain.